Magi are and always have been fairly strong against monks. But telepathy can be a problem if they leave the room.As long as they're prepped and hindered correctly the retardation thing should rarely be an issue.

Outside retardation they have big damage potential, and the new fire damage combos I think can scale up to dragon-level mitigation and stuff. But I went dormant shortly after Artificing so can't say for sure whether most go for retardation or for damage combos.

In terms of retardation, anyone with passive ents/effects is dangerous. But you may also outdamage them outside retardation. That being said, I believe certain Occultists will destroy you either way, biggest threat in my opinion. But I don't think anybody is good against an occultist, so...